Plasma spray coating design using phase and stress control

ABSTRACT

To manufacture a coating for an article for a semiconductor processing chamber, the article including a body of at least one of Al, Al 2 O 3 , or SiC is provided and a ceramic coating is coated on the body, wherein the ceramic coating includes a compound of Y 2 O 3 , Al 2 O 3 , and ZrO 2 . The ceramic coating is applied to the body by a method including providing a plasma spraying system having a plasma current in the range of between about 100 A to about 1000 A, positioning a torch standoff of the plasma spraying system a distance from the body between about 60 mm and about 250 mm, flowing a first gas through the plasma spraying system at a rate of between about 30 L/min and about 400 L/min, and plasma spray coating the body to form a ceramic coating, wherein splats of the coating are amorphous and have a pancake shape.

RELATED APPLICATIONS

This patent application claims the benefit under 35 U.S.C. §119(e) ofU.S. Provisional Application No. 61/994,648, filed May 16, 2014.

TECHNICAL FIELD

Embodiments of the present disclosure relate, in general, to ceramiccoated articles and to a process for applying a ceramic coating tocomponents.

BACKGROUND

In the semiconductor industry, devices are fabricated by a number ofmanufacturing processes producing structures of an ever-decreasing size.Some manufacturing processes such as plasma etch and plasma cleanprocesses expose a substrate to a high-speed stream of plasma to etch orclean the substrate. The plasma may be highly corrosive, and may corrodeprocessing chambers and other surfaces that are exposed to the plasma(e.g., exposed to a plasma environment). This corrosion may generateparticles, which frequently contaminate the substrate that is beingprocessed (e.g., semiconductor wafers). These on-wafer particles cancontribute to device defects.

As device geometries shrink, susceptibility to defects increases andparticle contaminant requirements become more stringent. Accordingly, asdevice geometries shrink, allowable levels of particle contamination maybe reduced. To minimize particle contamination introduced by plasma etchand/or plasma clean processes, chamber materials have been developedthat are resistant to plasmas. Different materials provide differentmaterial properties, such as plasma resistance, rigidity, flexuralstrength, thermal shock resistance, and so on. Also, different materialshave different material costs. Accordingly, some materials have superiorplasma resistance, other materials have lower costs, and still othermaterials have superior flexural strength and/or thermal shockresistance.

SUMMARY

In one embodiment an article includes a body comprising at least one ofAl, Al₂O₃, AlN, Y₂O₃, YSZ, or SiC. The article further includes aplasma-sprayed ceramic coating on at least one surface of the body, theceramic coating comprising a compound comprising Y₂O₃, Al₂O₃, and ZrO₂.The ceramic coating further comprises overlapping pancake-shaped splatsand has an amorphous phase.

In one embodiment, a method of coating an article includes setting aplasma current of a plasma spray system to a value of about 100 A toabout 1000 A. The method further includes positioning a torch standoffof the plasma spraying system a distance from a body between about 60 mmand about 250 mm. The method further includes flowing a first gasthrough the plasma spraying system at a rate of between about 30 L/minand about 400 L/min. The method further includes performing plasma spraycoating to from a ceramic coating on the body, the ceramic coatinghaving an internal compressive stress and an amorphous phase, whereinthe ceramic coating comprises a compound of Y₂O₃, Al₂O₃, and ZrO₂, andwherein splats of the coating are have a pancake shape.

In one embodiment an article is manufactured by a process that includesplacing a body comprising at least one of Al, Al₂O₃, AlN, Y₂O₃, YSZ, orSiC into a plasma spraying system (e.g., placing the article in front ofa nozzle or gun of the plasma spraying system) and performing a plasmaspray process by the plasma spraying system to coat at least one surfaceof the body with a ceramic coating composed of a compound comprisingY₄Al₂O₉ and a solid-solution of Y₂O₃—ZrO₂. The plasma spraying systemdeposits a ceramic coating made up of overlapping pancake-shaped splats.Additionally, the ceramic coating is formed directly in an amorphousphase without undergoing a phase change.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention is illustrated by way of example, and not by wayof limitation, in the figures of the accompanying drawings in which likereferences indicate similar elements. It should be noted that differentreferences to “an” or “one” embodiment in this disclosure are notnecessarily to the same embodiment, and such references mean at leastone.

FIG. 1 illustrates a cross-sectional view of a liner kit, in accordancewith one embodiment.

FIG. 2 illustrates an example architecture of a manufacturing system, inaccordance with one embodiment.

FIG. 3 illustrates a cross-sectional view of a plasma spray system, inaccordance with one embodiment.

FIG. 4 illustrates a method of applying a coating to an articleaccording to one embodiment.

FIG. 5 illustrates scanning electron microscope (SEM) views of splatsurfaces, in accordance with embodiments.

FIG. 6 illustrates curvature of coatings over time, in accordance withembodiments.

DETAILED DESCRIPTION

Embodiments of the invention are directed to an article (e.g., a plasmascreen, a liner kit, showerhead, lid, electrostatic chuck, or otherchamber components) exposed to plasma chemistry in a semiconductorprocessing chamber, and a ceramic coating on the article. A method ofcoating the article with the ceramic coating includes providing a plasmaspraying system having a plasma current in the range of between about100 A to about 1000 A, and positioning a torch standoff of the plasmaspraying system a distance from an article between about 50 mm and about250 mm. The method also includes flowing plasma gas (a gas that is usedto produce a plasma) through the plasma spraying system at a rate ofbetween about 30 L/min and about 400 L/min, and plasma spray coating thearticle with a ceramic coating. The ceramic coating includes a compoundof Y₂O₃, Al₂O₃, and ZrO₂, and splats of the coating on the article havea pancake shape. In one embodiment, the compound is a ceramic compoundcomprising Y₄Al₂O₉ and a solid-solution of Y₂O₃—ZrO₂. By performing theplasma spray process using the provided ceramics and the provided plasmaspray settings, the pancake shaped splats are created. These pancakeshaped splats cause the coating to have a dense and smooth surface withbuilt-in (internal) compressive stress. The ceramic coating can have athickness in a range from about 2 mil to about 15 mil.

In an embodiment, the ceramic coating includes about 53 mol % Y₂O₃,about 10 mol % ZrO₂, and about 37 mol % Al₂O₃. The plasma current can bein a range of between about 540 A and about 560 A, and the torchstandoff of the plasma spraying system can be positioned a distance fromthe body between about 90 mm and about 110 mm. In one embodiment, theplasma current is approximately 550 A and the distance from the body isabout 100 mm. The plasma gas can flow through the plasma spraying systemat a rate of between 30 L/min and about 400 L/min. In embodiments, anozzle of the torch can have an opening with a diameter of about 6 mm,the torch can have a raster speed of about 700 m/s, and a feed rate ofthe powder can be about 20 g/m.

Semiconductor chamber components, such as lids, liners, and processingkits can be coated with erosion resistant plasma spray coatings. Plasmaspray coatings can have built-in tensile stress that results in highporosity (e.g., greater than about 3 percent) and surface cracks thatcause an unacceptably high number of on-wafer particles. Further, due toinherent porosity in the coating, chemical attack during wet cleaningcan result in coating damage and/or peeling.

Coatings according to embodiments can provide dense and smooth surfaceswith built-in (internal) compressive stress, which can reduce inherentporosity and cracking in the coating and improve on-wafer defectperformance. Further, erosion resistance of coatings according toembodiments can be superior to standard coatings, which can increase theuseful lifetime of a component with the coating. For example, lidsformed of ceramic substrates with a coating according to embodiments canhave reduced porosity and cracking, leading to enhanced on-waferperformance. In another example, liners formed of metal substrates witha coating according to embodiments can be more resistant to damageresulting from chemical attacks during robust wet cleaning. In yetanother example, processing kit rings, which surround wafers duringprocessing and generally have high erosion rates, with coatingsaccording to embodiments can have smoother coatings with fewer or nocracks that enhance on-wafer particle performance.

According to embodiments, coatings can be formed by plasma spray to besmooth and dense by controlling coating phase and stress duringspraying. The powder for the plasma spraying can also be formulated tobe amorphous phase, rather than crystal phase, and have compressivestress during spraying. The powder materials can be formulated to easilyfully melt during coating deposition. Splats of the powder can beoptimized to a pancake shape without cracks or with fewer cracks bycontrolling the powder formulation, in addition to coating processconditions. A used herein, the term pancake-shaped refers to anapproximately circular, oval or oblong shape that has a diameter (orlength and width) that is many orders of magnitude larger than athickness.

In an embodiment, the coating can be primarily amorphous phase and maydevelop compressive evolving stress during spraying. During coatingdeposition, the fully melted particles can solidify to amorphous phasewithout a phase change. Avoiding a phase change during solidificationcan reduce the incidence of cracks forming due to coating volume change.Cracks in the splats of the coating can lead to poor coatingperformance, including increased numbers of on-wafer particles.

According to embodiments, substrate materials can include metal, metaloxides, nitrides, carbides, and alloys of these, such as Al, Al₂O₃, MN,SiC, Y₂O₃, yttria-stabilized zirconia (YSZ), etc.

Conductor etch processes can involve plasma assisted etching of aconductive substrate such as a Si wafer by a gas mixture. As shown inFIG. 1, in conductor etch, on-wafer level particle performance isprimarily correlated to chamber components such as a liner kit 100.Liner kit 100 has a front side 120, a back side 122, and an outerdiameter 124, which can include a chamber body 111, an upper liner 101,a slit valve door 103, a plasma screen 105 (i.e., the grill-likestructure around the wafer), a lower liner 107 and a cathode liner 109.The upper liner 101, slit valve door 103 and lower liner 107 are closerto the chamber body 111, whereas the plasma screen 105 is located arounda wafer (not shown, but located at position 130 during operation) andthe cathode liner 109 sits below the wafer.

A standard liner kit may be made up of an Al substrate coated with 8-12mil of plasma sprayed Y₂O₃ (yttria) or other ceramic with a surfaceroughness of about 100-270 μin. For most typical semiconductorapplications, an on-wafer particle specification is a maximum of about30 adders (e.g., 30 stray particles located on the wafer) at greaterthan or equal to 90 nm particle size. A standard Y₂O₃ liner kit meetsthis on-wafer particle specification.

For specific advanced applications at 28 nm device nodes, the on-waferparticle specification is much more stringent at less than or equal to1.3 adders at greater than or equal to 45 nm size. Moreover, theseapplications may use reducing chemistry (H₂, CH₄, CO, COS, etc), whichoften increases on-wafer particle contamination. Chamber tests usingconventional Y₂O₃ coated liner kits under reducing chemistry show highon-wafer particles (e.g., about 50 to 100 or more adders at greater thanor equal to 45 nm particle size). In some instances, significant chamberseasoning (e.g., 100 to 150 radio frequency RF hours of processing) canreduce the particle defect level down to about 0 to 10 adders at greaterthan or equal to 45 nm particle size to meet the productionspecifications before production can resume. However, long chamberseasoning times can reduce productivity. In tests, energy dispersiveX-ray spectroscopy has confirmed that conventional Y₂O₃-based on-waferparticles may originate from the liner kit. Further, Y₂O₃ coatings areless stable under reducing chemistry (e.g., H2, CH4, CO, COS, etc.) andform significant Y—OH. Y—OH conversion results in volume change whichresults in shed particles on the wafer.

Embodiments of the present invention include a composite ceramic coatingmaterial to improve on-wafer particle performance for chamber componentsin semiconductor industry applications. For example, in the liner kitapplication, the composite ceramic coating (e.g., a Yttria basedcomposite ceramic coating) may be applied to the plasma facing side ofthe liner kit using a plasma spray technique. In other embodiments, acomposite ceramic coating can be applied via aerosol deposition, slurryplasma, or other suitable techniques such as other thermal sprayingtechniques. In one example, the coating thickness on an Aluminum linerkit can be up to 15 mil. In another example, Al₂O₃ or other metal oxidesubstrates, where the coefficient of thermal expansion (CTE) of thecoating is better matched to the CTE of the substrate, can have athicker coating.

In an embodiment, the composite ceramic coating is composed of acompound of Y₂O₃, Al₂O₃, and ZrO₂. For example, in an embodiment, thecomposite ceramic coating includes about 53 mol % Y₂O₃, about 10 mol %ZrO₂, and about 37 mol % Al₂O₃. In another embodiment, the compositeceramic coating can include Y₂O₃ in a range of 20-90 mol %, ZrO₂ in arange of 0-80 mol % and Al₂O₃ in a range of 10-70 mol %. In otherembodiments, other distributions may also be used for the compositeceramic coating. In one embodiment, the composite ceramic is a yttriumoxide containing solid solution that may be mixed with one or more ofZrO₂, Al₂O₃, HfO₂, Er₂O₃, Nd₂O₃, Nb₂O₅, CeO₂, Sm₂O₃, Yb₂O₃, orcombination thereof. In one embodiment, the compound is a ceramiccompound comprising Y₄Al₂O₉ and a solid-solution of Y₂O₃—ZrO₂.

The composite ceramic coating may be created using a powder mixture andplasma spray parameters that produce splats with the previouslydescribed properties. These splats cause the composite ceramic coatingto have a built-in compressive stress. The built-in compressive stressis an internal compressive stress that is integrated into the ceramiccoating during the deposition process.

FIG. 2 illustrates an exemplary architecture of a manufacturing system200. The manufacturing system 200 may be a coating manufacturing system(e.g., for applying a composite ceramic coating to an article, such as aliner kit). In one embodiment, the manufacturing system 200 includesprocessing equipment 201 connected to an equipment automation layer 215.The processing equipment 201 may include a bead blaster 202, one or morewet cleaners 203, a plasma spray gun system 204 and/or other equipment.The manufacturing system 200 may further include one or more computingdevices 220 connected to the equipment automation layer 215. Inalternative embodiments, the manufacturing system 200 may include moreor fewer components. For example, the manufacturing system 200 mayinclude manually operated (e.g., off-line) processing equipment 201without the equipment automation layer 215 or the computing device 220.

Bead blaster 202 is a machine configured to roughen or smooth thesurface of articles (e.g., a liner kit). Bead blaster 202 may be a beadblasting cabinet, a hand held bead blaster, or other type of beadblaster. Bead blaster 202 may roughen a substrate by bombarding thesubstrate with beads or particles. In one embodiment, bead blaster 202fires ceramic beads or particles at the substrate. The roughnessachieved by the bead blaster 202 may be based on a force used to firethe beads, bead materials, bead sizes, distance of the bead blaster fromthe substrate, processing duration, and so forth. In one embodiment, thebead blaster uses a range of bead sizes to roughen the ceramic article.

In alternative embodiments, other types of surface rougheners than abead blaster 202 may be used. For example, a motorized abrasive pad maybe used to roughen the surface of ceramic substrates. A sander mayrotate or vibrate the abrasive pad while the abrasive pad is pressedagainst a surface of the article. A roughness achieved by the abrasivepad may depend on an applied pressure, on a vibration or rotation rateand/or on a roughness of the abrasive pad.

Wet cleaners 203 are cleaning apparatuses that clean articles (e.g., aliner kit) using a wet clean process. Wet cleaners 203 include wet bathsfilled with liquids, in which the substrate is immersed to clean thesubstrate. Wet cleaners 203 may agitate the wet bath using ultrasonicwaves during cleaning to improve a cleaning efficacy. This is referredto herein as sonicating the wet bath. In other embodiments, alternativetypes of cleaners such as dry cleaners may be used to clean thearticles. Dry cleaners may clean articles by applying heat, by applyinggas, by applying plasma, and so forth.

Ceramic coater 204 is a machine configured to apply a ceramic coating tothe surface of a substrate. In one embodiment, ceramic coater 204 is aplasma sprayer (or plasma spray system) that plasma sprays a coating(e.g., a composite ceramic coating) onto the substrate (e.g., a linerkit). In alternative embodiments, the ceramic coater 204 may apply otherthermal spraying techniques such as detonation spraying, wire arcspraying, high velocity oxygen fuel (HVOF) spraying, flame spraying,warm spraying and cold spraying may be used

The equipment automation layer 215 may interconnect some or all of themanufacturing machines 201 with computing devices 220, with othermanufacturing machines, with metrology tools and/or other devices. Theequipment automation layer 215 may include a network (e.g., a locationarea network (LAN)), routers, gateways, servers, data stores, and so on.Manufacturing machines 201 may connect to the equipment automation layer215 via a SEMI Equipment Communications Standard/Generic Equipment Model(SECS/GEM) interface, via an Ethernet interface, and/or via otherinterfaces. In one embodiment, the equipment automation layer 215enables process data (e.g., data collected by manufacturing machines 201during a process run) to be stored in a data store (not shown). In analternative embodiment, the computing device 220 connects directly toone or more of the manufacturing machines 201.

In one embodiment, some or all manufacturing machines 201 include aprogrammable controller that can load, store and execute processrecipes. The programmable controller may control temperature settings,gas and/or vacuum settings, time settings, etc. of manufacturingmachines 201. The programmable controller may include a main memory(e.g., read-only memory (ROM), flash memory, dynamic random accessmemory (DRAM), static random access memory (SRAM), etc.), and/or asecondary memory (e.g., a data storage device such as a disk drive). Themain memory and/or secondary memory may store instructions forperforming heat treatment processes described herein.

The programmable controller may also include a processing device coupledto the main memory and/or secondary memory (e.g., via a bus) to executethe instructions. The processing device may be a general-purposeprocessing device such as a microprocessor, central processing unit, orthe like. The processing device may also be a special-purpose processingdevice such as an application specific integrated circuit (ASIC), afield programmable gate array (FPGA), a digital signal processor (DSP),network processor, or the like. In one embodiment, programmablecontroller is a programmable logic controller (PLC).

In one embodiment, the manufacturing machines 201 are programmed toexecute recipes that will cause the manufacturing machines to roughen asubstrate, clean a substrate and/or article, coat a article and/ormachine (e.g., grind or polish) a article. In one embodiment, themanufacturing machines 201 are programmed to execute recipes thatperform operations of a multi-operation process for manufacturing aceramic coated article, as described with reference to figures below.The computing device 220 may store one or more ceramic coating recipes225 that can be downloaded to the manufacturing machines 201 to causethe manufacturing machines 201 to manufacture ceramic coated articles inaccordance with embodiments of the present disclosure.

FIG. 3 illustrates a cross-sectional view of a system 300 for plasmaspraying a coating on a dielectric etch component, or other article(e.g., a liner kit) used in a corrosive system. The system 300 is a typeof thermal spray system. In a plasma spray system 300, an arc 306 isformed between two electrodes, an anode 304 and a cathode 316, throughwhich a plasma gas 318 is flowing via a gas delivery tube 302. Theplasma gas 318 may be a mixture of two or more gases. Examples of gasmixtures suitable for use in the plasma spray system 300 include, butare not limited to, Argon/Hydrogen, Argon/Helium, Nitrogen/Hydrogen,Nitrogen/Helium, or Argon/Oxygen. The first gas (gas before theforward-slash) represents a primary gas and the second gas (gas afterthe forward-slash) represents a secondary gas. A gas flow rate of theprimary gas may differ from a gas flow rate of the secondary gas. In oneembodiment, a gas flow rate for the primary gas is about 30 L/min andabout 400 L/min. In one embodiment, a gas flow rate for the secondarygas is between about 3 L/min and about 100 L/min.

As the plasma gas is ionized and heated by the arc 306, the gas expandsand is accelerated through a shaped nozzle 320, creating a high velocityplasma stream.

Powder 308 is injected into the plasma spray or torch (e.g., by a powderpropellant gas) where the intense temperature melts the powder andpropels the material as a stream of molten particles 314 towards thearticle 310. Upon impacting the article 310, the molten powder flattens,rapidly solidifies, and forms a coating 312, which adheres to thearticle 310. The parameters that affect the thickness, density, androughness of the coating 312 include type of powder, powder sizedistribution, powder feed rate, plasma gas composition, plasma gas flowrate, energy input, torch offset distance, substrate cooling, etc. Asdiscussed with reference to FIG. 4, these parameters are optimized toform dense plasma sprayed coatings with built in compressive stress, inaccordance with embodiments.

FIG. 4 is a flow chart showing a process 400 for manufacturing a coatedarticle, in accordance with an embodiment. The operations of process 400may be performed by various manufacturing machines. The operations ofprocess 400 will be described with reference to any article as describedabove, which may be used in a reactive ion etch or plasma etch system.

At block 402, the powder for plasma spraying a coating is optimized.This may include optimization of powder composition, powder shape, andpowder size distribution for a composite ceramic coating. In oneembodiment, optimizing a coating includes, but is not limited to,determining powder type (e.g., chemical composition), average powdersize, and a powder feed rate. The powder type may be selected to producea coating as described previously. Raw ceramic powders having specifiedcompositions, purity and particle sizes can be selected. The ceramicpowder may be formed of Y₂O₃, Y₄Al₂O₉, Y₃Al₅O₁₂ (YAG), or other yttriacontaining ceramics. Additionally, ceramic powder may be combined withone or more of Y₂O₃, ZrO₂, Al₂O₃, HfO2, Er₂O₃, Nd₂O₃, Nb₂O₅, CeO₂,Sm₂O₃, Yb₂O₃, or other oxides and/or glass powders. The raw ceramicpowders are then mixed. In one embodiment, raw ceramic powders of Y₂O₃,Al₂O₃ and ZrO₂ are mixed together for the composite ceramic coating. Inone embodiment, the powder formulation is about 53 mol % Y₂O₃, 37 mol %Al₂O₃ and 10 mol % ZrO₂. These raw ceramic powders may have a purity of99.9% or greater in one embodiment. The raw ceramic powders may be mixedusing, for example, ball milling. After the ceramic powders are mixed,they may be calcinated at a specified calcination time and temperature.

In one embodiment, the ceramic powder includes 62.93 molar ratio (mol %)Y₂O₃, 23.23 mol % ZrO₂ and 13.94 mol % Al₂O₃. In another embodiment, theceramic powder can include Y₂O₃ in a range of 50-75 mol %, ZrO₂ in arange of 10-30 mol % and Al₂O₃ in a range of 10-30 mol %. In anotherembodiment, the ceramic powder can include Y₂O₃ in a range of 40-100 mol%, ZrO₂ in a range of 0-60 mol % and Al₂O₃ in a range of 0-10 mol %. Inanother embodiment, the ceramic powder can include Y₂O₃ in a range of40-60 mol %, ZrO₂ in a range of 30-50 mol % and Al₂O₃ in a range of10-20 mol %. In another embodiment, the ceramic powder can include Y₂O₃in a range of 40-50 mol %, ZrO₂ in a range of 20-40 mol % and Al₂O₃ in arange of 20-40 mol %. In another embodiment, the ceramic powder caninclude Y₂O₃ in a range of 70-90 mol %, ZrO₂ in a range of 0-20 mol %and Al₂O₃ in a range of 10-20 mol %. In another embodiment, the ceramicpowder can include Y₂O₃ in a range of 60-80 mol %, ZrO₂ in a range of0-10 mol % and Al₂O₃ in a range of 20-40 mol %. In another embodiment,the ceramic powder can include Y₂O₃ in a range of 40-60 mol %, ZrO₂ in arange of 0-20 mol % and Al₂O₃ in a range of 30-40 mol %. In otherembodiments, other distributions may also be used for the ceramicpowder.

In an embodiment, the powder is optimized to maintain an amorphous phaseduring plasma spraying. In an example, an amorphous phase can becontrolled by controlling the powder formulation. The special formulatedpowder can directly solidate to amorphous phase without phase change.

At block 404, the plasma spray parameters are optimized to maximizemelting of the powders, reduce the number of surface nodules, increasesplat surface, reduce roughness, and decrease porosity. Additionally,the plasma spray parameters are optimized to cause powder particles tobecome fully melted, and to cause these fully melted particles tosolidify into an amorphous phase without undergoing a phase change. Inembodiments, plasma spray parameters are optimized to produce pancakeshape splats of material during the plasma spraying. The pancake shapedsplats deposit over one another, building up many layers of pancakeshaped splats that forms a ceramic coating. In one embodiment,optimizing plasma spray parameters includes, but is not limited to,determining plasma gun power and composition of spray carrier gas.Optimizing the plasma spray parameters may also include determining aparticular spray coating sequence and process conditions for applying acoating (e.g., a composite ceramic coating) over a substrate (e.g., aplasma screen).

For example, Table A shows example coating process parameters to achievepancake shaped splats during plasma spraying.

TABLE A Coating Process Parameters To Produce Pancake-Shaped SplatsParameter Level 1 Torch F4 Primary gas flow rate (L/min) 45 Ar Secondarygas flow rate (%) 8 H₂ Plasma current (A) 550 Torch standoff distance(mm) 100 Powder injector (g/ml) 20 Raster Speed (mm/s) 700 NozzleDiameter (mm) 6

In one embodiment, the parameters are optimized to maximize melting,reduce the number of nodules (which can indicate an increase in meltingof powder), increase splat surface (which can indicate an increase inmelting of powder), reduce the surface roughness, and decrease theporosity of the coating, which will decrease the on-wafer particle countbecause particles are less likely to become dislodged. Additionally, theparameters are optimized to cause melted particles to solidify into theamorphous phase without undergoing a phase change.

For example, an optimized plasma current can be in the range of betweenabout 400 A to about 1000 A. A further optimized plasma current can bein the range of between about 500 A to about 800 A. In another example,an optimized positioning of a torch standoff of the plasma sprayingsystem can be a distance from the article (e.g., liner kit or plasmascreen) between about 50 mm and about 250 mm A further optimizedpositioning of a torch standoff can be a distance from the articlebetween about 70 mm and about 200 mm. In yet another example, optimizedgas flow through the plasma spraying system can be at a rate of betweenabout 40 L/min and about 400 L/min A further optimized gas flow throughthe plasma spraying system can be at a rate of between about 50 L/minand about 300 L/min.

At block 406, the article is coated according to the selectedparameters. Thermal spraying techniques and plasma spraying techniquesmay melt materials (e.g., ceramic powders) and spray the meltedmaterials onto the article using the selected parameters. The ceramicpowders may be fully melted during deposition, and may impact with atarget body to form relatively large pancake-shaped splats on the targetbody. The thermally sprayed or plasma sprayed ceramic coating may becomposed of a build-up of many overlapping pancake-shaped splats.Conceptually, the ceramic coating is made up of many layers ofoverlapping pancake shaped splats that form a single coating. Thethermally sprayed or plasma sprayed ceramic coating may have a thicknessabout 2-15 mil. The thickness, in one example, is selected according toan erosion rate of the composite ceramic coating to ensure that thearticle has a useful life of at least approximately 5000 Radio FrequencyHours (RFHrs) of exposure to a plasma environment, where RFHrs is ameasure of the number of hours that a component is used in processing.In other words, if the erosion rate of a composite ceramic coating isabout 0.005 mil/hr, then for a useful life of about 2500 RF hours, aceramic coating having a thickness of about 12.5 mil may be formed.

The plasma spray process may be performed in multiple spray passes. Foreach pass, the angle of a plasma spray nozzle may change to maintain arelative angle to a surface that is being sprayed. For example, theplasma spray nozzle may be rotated to maintain an angle of approximately45 degrees to approximately 90 degrees with the surface of the articlebeing sprayed.

In one embodiment, the plasma spray sequence can be optimized to achievean improved coating (e.g., less porosity, reduced surface nodules, largepancake shaped splats, and reduced surface roughness), as well as reducere-deposition of stray particles on to the coating surface (mostlycoming from backside coating of the article).

At block 408, plasma coating characterization may be performed. This mayinclude determining a surface morphology, a roughness, a porosity,identifying surface nodules, and so forth.

FIG. 5 shows illustrative scanning electron microscope (SEM) views ofsplats surfaces. View 501 shows splats of a coating on a 3000× zoomphoto (e.g., a 3000× scanning electron micrograph (SEM) of a one inchsample) with a 20 micron scale. View 502 shows splats of the coating ona 1000× zoom photo (e.g., a 1000× scanning electron micrograph (SEM) ofa one inch sample) with a 50 micron scale. View 503 shows splats of thecoating on a 500× zoom photo (e.g., a 500× scanning electron micrograph(SEM) of a one inch sample) with a 100 micron scale, according to anembodiment where the powder formulation and plasma spraying wereoptimized to form pancake shaped splats without cracks for the coating.View 504 shows splats of a coating on a 3000× zoom photo (e.g., a 3000×scanning electron micrograph (SEM) of a one inch sample) with a 20micron scale. View 505 shows splats of the coating on a 1000× zoom photo(e.g., a 1000× scanning electron micrograph (SEM) of a one inch sample)with a 50 micron scale. View 506 shows splats of the coating on a 500×zoom photo (e.g., a 500× scanning electron micrograph (SEM) of a oneinch sample) with a 100 micron scale, where the powder formulation andplasma spraying were not optimized to form pancake shaped splats withoutcracks for the coating.

As shown in FIG. 5, views 501, 502, and 503 of a coating optimized tohave pancake shaped splats show fewer or no cracks, as compared to views504, 505, and 506 of a coating. For example, pancake shaped splats canhave a disc like shape that is approximately round and flat. The splatsof views 501, 502, and 503 have smoother, crack-free, rounded edges anda more disk-like appearance than the splats of views 504, 505, and 506.Evaluations of coatings formed with powder and plasma spraying optimizedto form pancake shaped splats showed improved morphology and porosity ascompared to coating with splats of other shapes. For example, coatingsaccording to embodiments tend to have fewer nodules and more splats dueto improved melting of the powders, decreased roughness, and decreasedporosity, all of which contribute to improved on-wafer particleperformance.

FIG. 6 illustrates in-situ curvature change of a coating duringspraying, where graph 601 shows a comparative coating and graph 602shows a coating according to an embodiment. Curvature change is anindication of stress levels in a coating during spraying. Graph 601shows positive curvature change, which can indicate a tensile stress andcan be a result of the coating generally being of a more cubic phase.Graph 602 shows negative curvature change, which can indicate acompressive stress and can be a result of the coating generally being ofa more amorphous phase.

The preceding description sets forth numerous specific details such asexamples of specific systems, components, methods, and so forth, inorder to provide a good understanding of several embodiments of thepresent disclosure. It will be apparent to one skilled in the art,however, that at least some embodiments of the present disclosure may bepracticed without these specific details. In other instances, well-knowncomponents or methods are not described in detail or are presented insimple block diagram format in order to avoid unnecessarily obscuringthe present disclosure. Thus, the specific details set forth are merelyexemplary. Particular implementations may vary from these exemplarydetails and still be contemplated to be within the scope of the presentdisclosure.

Reference throughout this specification to “one embodiment” or “anembodiment” means that a particular feature, structure, orcharacteristic described in connection with the embodiment is includedin at least one embodiment. Thus, the appearances of the phrase “in oneembodiment” or “in an embodiment” in various places throughout thisspecification are not necessarily all referring to the same embodiment.In addition, the term “or” is intended to mean an inclusive “or” ratherthan an exclusive “or.” The terms “about” and “approximately” refer to avalue plus or minus 10%.

Although the operations of the methods herein are shown and described ina particular order, the order of the operations of each method may bealtered so that certain operations may be performed in an inverse orderor so that certain operation may be performed, at least in part,concurrently with other operations. In another embodiment, instructionsor sub-operations of distinct operations may be in an intermittentand/or alternating manner.

It is to be understood that the above description is intended to beillustrative, and not restrictive. Many other embodiments will beapparent to those of skill in the art upon reading and understanding theabove description. The scope of the disclosure should, therefore, bedetermined with reference to the appended claims, along with the fullscope of equivalents to which such claims are entitled.

What is claimed is:
 1. An article comprising: a body comprising at leastone of Al, Al₂O₃, MN, Y₂O₃, YSZ, or SiC; and a plasma-sprayed ceramiccoating on at least one surface of the body, the ceramic coatingcomprising a compound comprising Y₂O₃, Al₂O₃, and ZrO₂, the ceramiccoating further comprising a plurality of overlapping pancake-shapedsplats, wherein the ceramic coating has an amorphous phase.
 2. Thearticle of claim 1, wherein the ceramic coating comprises about 53 mol %Y₂O₃, about 10 mol % ZrO₂, and about 37 mol % Al₂O₃.
 3. The article ofclaim 1, wherein the ceramic coating has a composition selected from alist consisting of: 50-75 mol % of Y₂O₃, 10-30 mol % of ZrO₂, and 10-30mol % of Al₂O₃; 40-100 mol % of Y₂O₃, 0-60 mol % of ZrO₂, and 0-10 mol %of Al₂O₃; 40-60 mol % of Y₂O₃, 30-50 mol % of ZrO₂, and 10-20 mol % ofAl₂O₃; 40-50 mol % of Y₂O₃, 20-40 mol % of ZrO₂, and 20-40 mol % ofAl₂O₃; 70-90 mol % of Y₂O₃, 0-20 mol % of ZrO₂, and 10-20 mol % ofAl₂O₃; 60-80 mol % of Y₂O₃, 0-10 mol % of ZrO₂, and 20-40 mol % ofAl₂O₃; 40-60 mol % of Y₂O₃, 0-20 mol % of ZrO₂, and 30-40 mol % ofAl₂O₃; 30-60 mol % of Y₂O₃, 0-20 mol % of ZrO₂, and 30-60 mol % ofAl₂O₃; and 20-40 mol % of Y₂O₃, 20-80 mol % of ZrO₂, and 0-60 mol % ofAl₂O₃.
 4. The article of claim 1, wherein the ceramic coating has aninternal compressive stress.
 5. The article of claim 1, wherein thearticle comprises a liner kit comprising a front side, a back side, anupper liner, a slit valve door, a plasma screen, a lower liner and acathode liner.
 6. The article of claim 1, wherein a majority of thepancake-shaped splats are devoid of cracks.
 7. The article of claim 1,wherein the ceramic coating has a thickness of 2-15 mil and a usefullife of at least 5000 hours of processing in a plasma environment.
 8. Amethod comprising: setting, for a plasma spraying system, a plasmacurrent to a value of about 100 A to about 1000 A; positioning a torchof the plasma spraying system to a torch standoff distance from a bodybetween about 60 mm and about 250 mm; flowing a first gas through theplasma spraying system at a rate of between about 30 L/min and about 400L/min; and performing plasma spray coating to from a ceramic coating onthe body, the ceramic coating having an internal compressive stress andan amorphous phase, wherein the ceramic coating comprises a compound ofY₂O₃, Al₂O₃, and ZrO₂, and wherein splats of the ceramic coating have apancake shape.
 9. The method of claim 8, wherein the ceramic coatingcomprises about 53 mol % Y₂O₃, about 10 mol % ZrO₂, and about 37 mol %Al₂O₃.
 10. The method of claim 8, wherein the ceramic coating has acomposition selected from a list consisting of: 50-75 mol % of Y₂O₃,10-30 mol % of ZrO₂, and 10-30 mol % of Al₂O₃; 40-100 mol % of Y₂O₃,0-60 mol % of ZrO₂, and 0-10 mol % of Al₂O₃; 40-60 mol % of Y₂O₃, 30-50mol % of ZrO₂, and 10-20 mol % of Al₂O₃; 40-50 mol % of Y₂O₃, 20-40 mol% of ZrO₂, and 20-40 mol % of Al₂O₃; 70-90 mol % of Y₂O₃, 0-20 mol % ofZrO₂, and 10-20 mol % of Al₂O₃; 60-80 mol % of Y₂O₃, 0-10 mol % of ZrO₂,and 20-40 mol % of Al₂O₃; 40-60 mol % of Y₂O₃, 0-20 mol % of ZrO₂, and30-40 mol % of Al₂O₃; 30-60 mol % of Y₂O₃, 0-20 mol % of ZrO₂, and 30-60mol % of Al₂O₃; and 20-40 mol % of Y₂O₃, 20-80 mol % of ZrO₂, and 0-60mol % of Al₂O₃.
 11. The method of claim 8, wherein the plasma current isin a range of between about 450 A and about 800 A.
 12. The method ofclaim 8, wherein the torch standoff distance of the plasma sprayingsystem is between about 60 mm and about 200 mm.
 13. The method of claim8, wherein a majority of the splats having the pancake shape are devoidof cracks.
 14. The method of claim 8, wherein the first gas is a primarygas of a gas mixture comprising the primary gas and a secondary gas,wherein the gas mixture is selected from a list consisting of: a mixtureof Argon and Hydrogen, a mixture of Argon and Helium, a mixture ofNitrogen and Hydrogen, a mixture of Nitrogen and Helium, and a mixtureof Argon and Oxygen.
 15. The method of claim 14, wherein the first gasis flowed through the plasma spraying system at a rate of between 35L/min and about 300 L/min.
 16. The method of claim 14, wherein thesecondary gas is flowed through the plasma spraying system at a rate ofbetween about 3 L/min and about 100 L/min.
 17. The method of claim 8,wherein the splats solidify in the amorphous phase without undergoing aphase change.
 18. The method of claim 8, wherein the plasma sprayingsystem that performs the plasma spray coating has a nozzle diameter ofabout 6 m.
 19. An article comprising: a body; and a plasma-sprayedceramic coating on at least one surface of the body, the ceramic coatingcomprising a compound comprising Y₄Al₂O₉ and a solid-solution ofY₂O₃—ZrO₂, the ceramic coating further comprising a plurality ofoverlapping pancake-shaped splats, wherein the ceramic coating has anamorphous phase and internal compressive stress.
 20. The article ofclaim 19, wherein a majority of the pancake-shaped splats are devoid ofcracks, and wherein the ceramic coating has a thickness of 2-15 mil.